1. Field of the Invention
The present invention relates to a protective cap for covering a row of nozzles open in an ejection surface of a recording head, such that a closed or sealed space is defined inside the protective cap. The invention also relates to an inkjet recording apparatus including the protective cap, and a method of producing the protective cap.
2. Description of Related Art
There is known an inkjet recording apparatus including a recording head and a protective cap. The recording head has an ejection surface in which open ends of a plurality of nozzles are arranged in a row. Droplets of ink supplied from a sub tank are selectively ejected from the row of nozzles to record an image on a recording medium. The protective cap is brought into contact with the ejection surface to hermetically cover the nozzle row.
As such a protective cap, there is used a type as disclosed in FIG. 4 of JP-A-2001-80091, which includes a mainbody and a lip portion that are integrally formed of rubber. The mainbody has a protruding portion configured to have a recess inside thereof, and the lip portion is disposed around the recess. When the protective cap covers the nozzle row, the lip portion directly and closely contacts the ejection surface, and a sealed space is defined inside the protruding portion.
The hardness of the rubber forming the mainbody and the lip portion is set at 30-40 Hs JIS A. Throughout this specification and in the appended claims, hardness is defined in accordance with JIS (Japanese Industrial Standards) K 6301. This value is appropriate for preventing occurrence of a clearance between the ejection surface and the lip portion, and deformation of the protruding portion at the same time. That is, when the hardness of the lip portion is too high, the clearance tends to occur. On the other hand, when the hardness of the lip portion is too low, the protruding portion tends to collapse or deform.
Since the mainbody and the lip portion of the protective cap are integrally formed of rubber, when a sucking operation to eliminate or prevent clogging of the nozzles is implemented, a negative pressure is produced in the recess or at the sealed space to cause the lip portion to deform or collapse, thereby closing open ends of the nozzles.
In view of this, there has been proposed a protective cap where a mainbody is formed of synthetic resin and a lip portion is formed of rubber, as disclosed in FIG. 3 of the above-mentioned publication, for instance. The mainbody includes a base portion and a protruding portion extending from the base portion and integrally formed with the base portion. The lip portion is disposed on the protruding portion of the mainbody to cover at least an upper portion of the protruding portion. According to this protective cap, the lip portion of the protective cap does not deform or collapse during the sucking operation, and thus the hermeticity of the sealed space is ensured more stably and reliably.
However, the conventional protective cap is disadvantageous in that the mainbody and the lip portion tend to separate from each other at the interface thereof, since the mainbody and the lip portion are formed of different materials, namely, the mainbody is formed of synthetic resin and the lip portion is formed of rubber.
This disadvantage can be overcome by forming the protruding portion and the lip portion such that the protruding portion has a boss or a hole that engage with a part of the lip portion when the mainbody and the lip portion are assembled. However, this undesirably leads to a complex shape of a mold that is used to form the mainbody.
Further, such a protective cap requires a large number of production steps and pushes up the cost, for the following reasons. That is, since the mainbody and the lip portion are formed of different materials, two molds for forming the mainbody and the lip portion, respectively, should be prepared, accordingly increasing the production cost. More specifically, the protective cap is produced such that the mainbody is formed by injecting a resin material into a mold prepared specially for forming the mainbody, then the thus formed mainbody of resin is taken off the mold and put into another mold prepared specially for forming the lip portion, to form the lip portion by injecting a rubber material into the latter mold. In this way, two production steps are required for producing the protective cap, increasing the number of production steps and accordingly the production cost.